Install SSE v2.4 and the Chat Bubbles mod in a MC 1.15.x Fabric profile.
Start MC and go into your keybindings settings (or any other GUI which is scrollable, e.g. the modmenu one, if enough mods are installed).
Notice the 2-5 seconds hang. It only occurs the first time you open such a scrollable UI though, after that it works fine until you restart the game again.
Notes:
The Chat Bubbles mod seems unsupported, I know. But the latest version still works with 1.15.x, and it also works with SSE v2.3. It may not be that easy to figure out what caused it, as Chat Bubbles is closed source, but judging from the very few changes v2.4 actually made, maybe you can find the time to figure it out. Thanks!
Steps to reproduce:
Notes: The Chat Bubbles mod seems unsupported, I know. But the latest version still works with 1.15.x, and it also works with SSE v2.3. It may not be that easy to figure out what caused it, as Chat Bubbles is closed source, but judging from the very few changes v2.4 actually made, maybe you can find the time to figure it out. Thanks!