Hiya!
Utter newbie plugin developer here — and I’ve already seen that this is far more than I can swallow at this time 
Soooo I managed so far to…
- figure out how to ‘compile’ the plugin using `npm` — it took me way longer than hinted on the ‘generate’ README, mostly because those instructions are seriously outdated by several generations (pun intended!). The current Joplin docs suggest doing everything with `yarn` as package manager anyway…
- figure out what exactly to put into the filepath for the ‘in development’ plugin
That resulted into a new plugin showing up, marked as `DEV` — so far, so good — but everything in it is greyed out. No additional preferences/menus are shown anywhere.
On this thread, ‘entering developer mode’ is mentioned. Now I had never ever done that before, bit it sort of worked. It seems that it starts with a brand new environment — all notes are gone, all my configurations are gone, etc. I guess that’s how it’s supposed to work. Oh well.
The new plugin shows up as before, marked as `DEV`, but, again, everything in it is still greyed out. And still no additional preferences/menus are shown anywhere. So… ‘nothing works’.
Now… one very good reason for LT not really working might be the lack of an API key. It seems that LT now only generates API keys for paying customers. It makes sense: if you wish to do more and need an API key, but don’t wish to get charged extra for that awesome privilege, well, it’s all open source, so you can simply download it to your favourite host (or locally) and just do whatever you wish there. However, I was expecting that, by default, this plugin would still do something useful using the free access API.
Needless to say, I did not install the LanguageTool Server. It’s developed in Java. Sorry, but no, thank you! I had already too many bad experiences with Java in the past three decades — enough is enough!
That said, I wonder where exactly — or what exactly — I need to click to ‘activate’ the plugin somehow. `DEV` plugins don’t seem to be the cute on/off slider, so I don’t have any easy way of knowing if anything works at all. Probably I might get some hints on the dev tools console?… What would you recommend that I try next?