After connecting to the Win11-PC there were 2 updates available, 28.33 and a second one I do not remember. I hit "install all" (German system), it took several minutes and said "everything was successfully updated". Though the version is displayed still with 28.20
Only after disconnecting from the PC the 1050 said "28.33 available" on the display and the update could be started manually.
Really, Garmin? The 1050 is going to be the worst piece of electronics I ever bought.