A lot of things changed, and things will change. If you do not want things to change then do not upgrade.
When I run 25.03 I get the same font dialog as I see in version 26.2 with respect to Bahnschrift
I do not recall or find that we did anything different here between those versions, but the Qt version did change. And maybe in your language the behavior changed between versions.
Now, we are changing behavior in the next version to fix actually using any style other than bold or italic: