With current f38 beta texlive-memoir-svn65040-65.fc38.noarch,

> $ cat test.tex
> \documentclass{memoir}
> \begin{document}
> \end{document}

> $ latex test
> This is pdfTeX, Version 3.141592653-2.6-1.40.24 (TeX Live 2022) (preloaded format=latex)
>  restricted \write18 enabled.
> 
> kpathsea: Running mktexfmt latex.fmt
> mktexfmt: mktexfmt is using the following fmtutil.cnf files (in precedence order):
> mktexfmt:   /usr/share/texlive/texmf-dist/web2c/fmtutil.cnf
> mktexfmt: mktexfmt is using the following fmtutil.cnf file for writing changes:
> mktexfmt:   /home/sbergman/.texlive2022/texmf-config/web2c/fmtutil.cnf
> mktexfmt [INFO]: writing formats under /home/sbergman/.texlive2022/texmf-var/web2c
> mktexfmt [INFO]: --- remaking latex with pdftex
> mktexfmt: running `pdftex -ini   -jobname=latex -progname=latex -translate-file=cp227.tcx *latex.ini' ...
> This is pdfTeX, Version 3.141592653-2.6-1.40.24 (TeX Live 2022) (INITEX)
>  restricted \write18 enabled.
>  (/usr/share/texlive/texmf-dist/web2c/cp227.tcx)
> entering extended mode
> (/usr/share/texlive/texmf-dist/tex/latex/latexconfig/latex.ini
> (/usr/share/texlive/texmf-dist/tex/generic/tex-ini-files/pdftexconfig.tex)
> (/usr/share/texlive/texmf-dist/tex/latex/base/latex.ltx
> (/usr/share/texlive/texmf-dist/tex/latex/base/texsys.cfg)
> ./texsys.aux found
> 
> 
> \@currdir set to: ./.
> 
> 
> Assuming \openin and \input 
> have the same search path.
> 
> 
> Defining UNIX/DOS style filename parser.
> 
> catcodes, registers, parameters,
> LaTeX2e <2022-06-01> patch level 5
> (/usr/share/texlive/texmf-dist/tex/latex/l3kernel/expl3.ltx
> (/usr/share/texlive/texmf-dist/tex/latex/l3kernel/expl3-code.tex)) hacks,
> document commands, control, par, spacing, files, font encodings, lengths,
> ====================================
> 
> Local config file fonttext.cfg used
> 
> ====================================
> (/usr/share/texlive/texmf-dist/tex/latex/base/fonttext.cfg
> (/usr/share/texlive/texmf-dist/tex/latex/base/fonttext.ltx
> === Don't modify this file, use a .cfg file instead ===
> 
> (/usr/share/texlive/texmf-dist/tex/latex/base/omlenc.def)
> (/usr/share/texlive/texmf-dist/tex/latex/base/omsenc.def)
> (/usr/share/texlive/texmf-dist/tex/latex/base/ot1enc.def)
> (/usr/share/texlive/texmf-dist/tex/latex/base/t1enc.def)
> (/usr/share/texlive/texmf-dist/tex/latex/base/ts1enc.def)
> (/usr/share/texlive/texmf-dist/tex/latex/base/ts1cmr.fd)
> (/usr/share/texlive/texmf-dist/tex/latex/base/t1cmr.fd)
> (/usr/share/texlive/texmf-dist/tex/latex/base/ot1cmr.fd)
> (/usr/share/texlive/texmf-dist/tex/latex/base/ot1cmss.fd)
> (/usr/share/texlive/texmf-dist/tex/latex/base/ot1cmtt.fd)))
> ====================================
> 
> Local config file fontmath.cfg used
> 
> ====================================
> (/usr/share/texlive/texmf-dist/tex/latex/base/fontmath.cfg
> (/usr/share/texlive/texmf-dist/tex/latex/base/fontmath.ltx
> === Don't modify this file, use a .cfg file instead ===
> 
> (/usr/share/texlive/texmf-dist/tex/latex/base/omlcmm.fd)
> (/usr/share/texlive/texmf-dist/tex/latex/base/omscmsy.fd)
> (/usr/share/texlive/texmf-dist/tex/latex/base/omxcmex.fd)
> (/usr/share/texlive/texmf-dist/tex/latex/base/ucmr.fd)))
> ====================================
> 
> Local config file preload.cfg used
> 
> =====================================
> (/usr/share/texlive/texmf-dist/tex/latex/base/preload.cfg
> (/usr/share/texlive/texmf-dist/tex/latex/base/preload.ltx)) page nos., x-ref,
> environments, center, verbatim, math definitions, boxes, title, sectioning,
> contents, floats, footnotes, index, bibliography, output,
> ===========================================
> Local configuration file hyphen.cfg used
> ===========================================
> (/usr/share/texlive/texmf-dist/tex/generic/babel/hyphen.cfg
> (/usr/share/texlive/texmf-dist/tex/generic/hyphen/hyphen.tex)
> (/usr/share/texlive/texmf-dist/tex/generic/hyphen/dumyhyph.tex)
> (/usr/share/texlive/texmf-dist/tex/generic/hyphen/zerohyph.tex))
> (/usr/share/texlive/texmf-dist/tex/generic/pdftex/glyphtounicode.tex)
> (/usr/share/texlive/texmf-dist/tex/latex/base/utf8.def
> (/usr/share/texlive/texmf-dist/tex/latex/base/omsenc.dfu)
> (/usr/share/texlive/texmf-dist/tex/latex/base/ot1enc.dfu)
> (/usr/share/texlive/texmf-dist/tex/latex/base/t1enc.dfu)
> (/usr/share/texlive/texmf-dist/tex/latex/base/ts1enc.dfu))
> (/usr/share/texlive/texmf-dist/tex/latex/firstaid/latex2e-first-aid-for-externa
> l-files.ltx)
>  ) )
> Beginning to dump on file latex.fmt
>  (preloaded format=latex 2023.3.15)
> 21873 strings of total length 407164
> 1847976 memory locations dumped; current usage is 204&343527
> 20160 multiletter control sequences
> \font\nullfont=nullfont
> \font\c__fp_exp_intarray=cmr10 at 0.00002pt
> \font\c__fp_trig_intarray=cmr10 at 0.00003pt
> \font\c_initex_cctab=cmr10 at 0.00005pt
> \font\c_other_cctab=cmr10 at 0.00006pt
> \font\c_str_cctab=cmr10 at 0.00008pt
> \font\g__regex_state_active_intarray=cmr10 at 0.00009pt
> \font\g__regex_thread_info_intarray=cmr10 at 0.0001pt
> \font\g__regex_submatch_prev_intarray=cmr10 at 0.00012pt
> \font\g__regex_submatch_begin_intarray=cmr10 at 0.00014pt
> \font\g__regex_submatch_end_intarray=cmr10 at 0.00015pt
> \font\g__regex_submatch_case_intarray=cmr10 at 0.00017pt
> \font\g__regex_balance_intarray=cmr10 at 0.00018pt
> \font\g__codepoint_uppercase_index_intarray=cmr10 at 0.0002pt
> \font\g__codepoint_lowercase_index_intarray=cmr10 at 0.00021pt
> \font\g__codepoint_uppercase_blocks_intarray=cmr10 at 0.00023pt
> \font\g__codepoint_lowercase_blocks_intarray=cmr10 at 0.00024pt
> \font\OMX/cmex/m/n/10=cmex10
> \font\tenln=line10
> \font\tenlnw=linew10
> \font\tencirc=lcircle10
> \font\tencircw=lcirclew10
> \font\OT1/cmr/m/n/5=cmr5
> \font\OT1/cmr/m/n/7=cmr7
> \font\OT1/cmr/m/n/10=cmr10
> \font\OML/cmm/m/it/5=cmmi5
> \font\OML/cmm/m/it/7=cmmi7
> \font\OML/cmm/m/it/10=cmmi10
> \font\OMS/cmsy/m/n/5=cmsy5
> \font\OMS/cmsy/m/n/7=cmsy7
> \font\OMS/cmsy/m/n/10=cmsy10
> \font\c_code_cctab=cmr10 at 0.00026pt
> \font\c_document_cctab=cmr10 at 0.00027pt
> 512280 words of font info for 32 preloaded fonts
> 14 hyphenation exceptions
> Hyphenation trie of length 6081 has 183 ops out of 35111
>   2 for language 1
>   181 for language 0
> 0 words of pdfTeX memory
> 0 indirect objects
> No pages of output.
> Transcript written on latex.log.
> mktexfmt [INFO]: log file copied to: /home/sbergman/.texlive2022/texmf-var/web2c/pdftex/latex.log
> mktexfmt [INFO]: /home/sbergman/.texlive2022/texmf-var/web2c/pdftex/latex.fmt installed.
> mktexfmt [INFO]: successfully rebuilt formats: 1
> mktexfmt [INFO]: not selected formats: 19
> mktexfmt [INFO]: total formats: 20
> mktexfmt [INFO]: 
> *************************************************************
> *                                                           *
> * WARNING: you are switching to fmtutil's per-user formats. *
> *         Please read the following warnings!               *
> *                                                           *
> *************************************************************
> 
> You have run fmtutil-user (as opposed to fmtutil-sys) for the first time;
> this has created format files which are local to your personal account.
> 
> From now on, any changes in system formats will *not* be automatically
> reflected in your files; furthermore, running fmtutil-sys will no longer
> have any effect for you.
> 
> As a consequence, you yourself have to rerun fmtutil-user after any
> change in the system directories. For example, when one of the LaTeX or
> other format source files changes, which happens frequently.
> See https://tug.org/texlive/scripts-sys-user.html for details.
> 
> If you want to undo this, remove the files mentioned above.
> 
> Run mktexfmt --help for full documentation of fmtutil.
> mktexfmt [INFO]: exiting with status 0
> entering extended mode
> (./test.tex
> LaTeX2e <2022-06-01> patch level 5
> L3 programming layer <2022-12-17>
> ! Use of \@tempa doesn't match its definition.
> <inserted text> u
>                  ndefined
> l.2 \begin
>           {document}
> ? 

Instead trying a `\documentclass{article}` succeeds.  (But it also prints the "WARNING: you are switching to fmtutil's per-user formats." blob.  Which also appears to be new with this version of texlive.  And which leaves me without a clue what, if anything, I should do about it.)