Firefox automatically appends .com if no domain is given - Question | Mozilla Support
https://support.mozilla.org/en-US/questions/958926
browser.fixup.alternate.enabled でよさそう
> Instead of using pre-configured DH groups, or generating their own with "openssl dhparam", operators should use the pre-defined DH groups ffdhe2048, ffdhe3072 or ffdhe4096 recommended by the IETF in [RFC 7919 https://tools.ietf.org/html/rfc7919]. These groups are audited and may be more resistant to attacks than ones randomly generated.
mstdn.rinsuki.net とか mstdn.maud.io が死んだときの避難用