I know of 7-8 different novel sites, but the main 3 is, as usual, SH, WN, and RR
Webnovel is of course, webnovel. Post here only to avoid having anything and everything plagiarized. As much crap as people give the contracts, if you don't expect to just hit it big, and are willing to put up with schedules and deadlines, WN's contracts are actually about the norm for an online writing contract. And if you dislike the terms, but you start bringing in a certain amount of revenue, you will be allowed to renegotiate the terms. More money means more say in outcomes.
SH. Friendly sure. Professional? Absolutely not. Scribblehub is where you should go if you are concerned with critical reviews and have thin skin and can't handle someone being brutally honest. It is not where you go to improve, because the bar is extremely low here. It's a good place for hobbyists, but not for people who want to do something with writing that involves monetary compensation or whatever. Still, it's by far the best site for casualists.
RoyalRoad. By far the best of the 3 if you want to do something with your writing besides hobbyism (writing for yourself etc.). Has the highest standards, and the best results when it comes to critical reviews. They have a large community of genuinely knowledgeable editors, though you'll have to ask around in the forums to get in contact with them if you don't want to wait for them to find you, which is a fairly unreliable tactic. People complain about its views on LGBTQ, but this is nonsense. I admit it lacks much in the way of a Yaoi/BL scene, but it has just as many if not more Yuri/Gender Bender novels present, and quite a few of them are highly ranked. So saying it is unfriendly to LGBTQ is inaccurate and false. It just favors one side of LGBTQ more.
The only thing people tend to dislike in RR when it comes to Yuri/Yaoi, is that people spring it up in the story without mentioning it will happen in the synopsis or warnings or something. I agree with this. You should give some kind of forewarning or briefly mention that it will be present in your story beforehand. Or even hint at it in the synopsis, which is the most common form used in RR. Do that, and you'll be fine for the most part. Don't do that, and you'll likely get criticism. I don't see the problem. Pure laziness if you don't and still complain.
And just going to toss in Wattpad as an honorable mention. It's a dumpster fire. I used to frequent it back when it had an active forum. It was actually not a bad site. In fact, I was part of a now-defunct site called Figment, that was HarperCollins owned, but was shutdown. The userbase of Figment is split in two. One half went to a place called GetUnderlined, the rest migrated to Wattpad. This was Wattpad's heydey to me, circa 2014-2016. The way it is now....if you don't write smut(mostly from a female perspective) or something do with werewolves and vampires...you won't get much traction. Though I have noticed a recent upsurge in female Protags being assassins/gangsters/etc. on that site lately...not sure what that's about.
A few people I know from Figment, were also from another defunct site called Inkpop, which has always been by far my favorite site. I would still be there and only there if Inkpop was still around. Other sites that I know people in is Mibba, Fictionpress, Honeyfeed, CreativeNovels, Foxteller, Neoread, and Moonquill. Fictionpress was my first site ever and I spent 4 years being apart of a very active community there, though most of us migrated to a Skype chat channel, and then to Discord. After we left, Fictionpress has gotten kind of quiet. It has a community that still regularly posts, but thats all I know, mostly in the Manga, Action, and Fantasy sections. The Adventure section kind of died down though it still has some movement. One of the two first authors I ever became followers to were both originally from Fictionpress, one being a guy named Rental and a girl named Eytha. Rental is....gone. Eytha surfaces from time to time.