I can recommend it for a Windows/Linux/Android hybrid environment from personal experience
Personally I think it's silly that the definition of "internet" has shifted so much over the past few years that "it's not HTTP" is now seen as a downside. The internet has finally become the BTX/Telex-style server/client network it was designed to replace.
In fact, I'm fighting right now with my ISP (O2). They don't want to sell me a business connection. At the same time, they intentionally degrade service to prevent me from hosting services on my private connection. That includes forcefully closing PPPoE connections every 24h, assigning a random new IPv6 range every 24h (but with a valid_lft of 1.438 billion seconds), etc. But they do offer 10 consecutive phone numbers with 3x concurrent calling for private contracts.
I don't have an IP where i can just run Quassel on 443. Using it over websockets on a subdomain might indeed solve my troubles.
it works well indeed, i run an instance of quassel-core on a VPS for many years and connect to it through wireguard tunnel exclusively (fits nicer in my overall scheme of accessing my services)