I don't know if cross-platform applications are very popular anymore. Most of the good software I use is either single platform using native code, or it's Qt or it's electron. Only rare cases use something else.
Sublime has their own cross-platform native widget system
Jetbrains/minecraft use Java
Spotify is chromium, discord is chromium, thunderbird is firefoxium, Obsidian is chromium, steam is (probably?) chromium.
Most software that I know is cross-platform uses Qt otherwise; qbittorrent (duh), Transmission, KeepassXC, VLC (mostly, but also uses other GUI frameworks sometimes), Calibre, Krita, OBS
Sublime has their own cross-platform native widget system
Jetbrains/minecraft use Java
Spotify is chromium, discord is chromium, thunderbird is firefoxium, Obsidian is chromium, steam is (probably?) chromium.
Most software that I know is cross-platform uses Qt otherwise; qbittorrent (duh), Transmission, KeepassXC, VLC (mostly, but also uses other GUI frameworks sometimes), Calibre, Krita, OBS