Most frontends (I don't know any, really) doesn't allow you to set a default language for your post. For that reason, a lot of frontends allow you to post without any language selected, while defaulting to English. But that is not universally true. Photon recently started requiring language to be selected and started defaulting to Undetermined language. This now creates unnecessary friction when the community doesn't have it as allowed language and requires the user to select allowed language for every single post.
It really is a simple change on your end that will take you seconds, but can save a lot of time in the long run and some frustration for people that want to post in your communities.
On lemmy-ui frontend you can change it by going to community settings and under languages you can select multiple ones by holding Ctrl key.
P.S. This community is a great example of one that doesn't allow Undetermined language.
In the next version or the one after that, I believe it will default to your browser/system language. The undetermined language thing isn't actually good for anyone.
Least of all, people finding communities in their tongue.
If Sync ever updates, I hope it adds language to the post form.
Oof, I feel like that'll cause a lot of English comments to be marked with the speaker's native language
this is only for setting the default user language during registration based on the browsers accept language headers.
How is it bad? I never said it was good, I said it's a friction point with a zero cost solution until setting default language for posts becomes available on all clients.
Language specific instances can already set allowed languages on instance-level that can't be overwritten by communities, so it's a non-issue.
One of the things that really make sense but might be overkill is to have integration with any of the open source Large Language Models. The client could wouldn't have to ask the user or rely or system settings, and autodetect the language. Depending on the content, it would even make sense to have some override system (e.g, I am not fluent in Spanish, but I would be interested in seeing football news from La Liga directly in Spanish without having to wait for the UK newspapers to pick it up)