(Sorry to hijack your thread) I am new to Kodi.
Since day1 with a brand new RPi5 + wired gigabit LAN, I experience a similar type of slowness issue. Using LE 12.0.1 and SMB via Windows 10 home server. Folders (even small 1-2 files in it) usually open under 2-3 seconds (which is still somewhat slow, heck its on a gigabit LAN!). But what worries me more, during these 2-3 seconds, basically the UI blocks any other input action. If the delay is more, the UI block is more noticeable. Sometimes the circling happens for a minute (I cannot confirm if its due to the slow SMB or something completely different stuck in the background reason). Then suddenly all inputs I entered in the past 1 minute gets processed in a split second. Looks crazy I can tell you.
Is that something sort of "get used to it, it works like that since xbmc 2001" and normal in the Kodi universe @ 2024? Or Kodi v21 is very new, contains too much experimental and untested stuff?