I think this was caused by this PR https://github.com/radzenhq/radzen-blazor/pull/1129/files
Noticed the issue when I updated to 4.15.8. l confirmed Radzen.Blazor 4.15.7 does not have the issue.
No code change on my end to cause this other than the package update.
Looks like in my css file the .rz-grid-filter-icon class still has :after{content:'filter_alt'} on it
Do I need to update the css manually?
Yes, indeed my css is locally hosted, so I'll need to update it.
same for me, thanks for posting your solution.
This also worked for me.
