Since Server 2019 (Windows 10 multi user), Windows Search support per-user search indexes, thus enabling search roaming is not advised.
Only until server 2016 this was required. I have set up an amount of RDS environments including windows 10 multi user (AVD).
Article:
https://video2.skills-academy.com/en-us/fslogix/configure-search-roaming-ht
Quote:
FSLogix 2201 and newer do not allow FSLogix Search roaming on versions of Windows that natively provide per-user search indexes. Per-user search indexes are natively supported by Windows Server 2019 version 1809 and newer, as well as all versions of Windows 10 multi-session and Windows 11 multi-session.