Cannot use hunspell French dictionaries

[jphbutler64]

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Environment

Linux Ubuntu 22.04.2 LTS
vale version 2.28.0
Hunspell 1.7.0
dictionaries supplied with the linux distro

Describe the bug / provide steps to reproduce it

The standard French dictionaries fr_FR, fr_CH etc do not work with vale.

Using this configuration:

extends: spelling
message: "'%s' is a typo"
dicpath: /usr/share/hunspell
dictionaries:
    - fr_FR

yields:

E201 Invalid value [/home/jpbutler/styles/philip/Basic.yml:1:1]:
   1* extends: spelling
   2  message: "'%s' is a typo"
   3  dicpath: /usr/share/hunspell
NOSUGGEST stanza had more than one flag: "--"
Execution stopped with code 1.

The English dictionaries work fine with my vale setup, and the French dictionaries work well with hunspell.
fr_FR.dic contains 586 lines with -- as part of the description of the inflexions (out of 84140 entries). fr_FR.aff
contains a single line with --, which is NOSUGGEST --.

As a workaround, I removed all -- lines in the dic and aff lines, but I then loose an awful lot inflections, making eg. all plurals unrecogniosable in vale and missing many of the most common invariant words etc. I have also tried replacing -- with £, @ or ~, in th e dic and aff files, but without any luck either.