Note that this ^ is a one-way upgrade as the RPi5 kernel that LE is using will not boot an RPi4. It's not impossible to recover from (mount and overwrite some files with the RPi4 image equivalents) but .. that's fiddly.
So, i will order a Pi 5 + new Power Suppy on Monday. This will replaced my PI 4 with LE 11.0.3.
To upgrade:
- Full Backup
- Upload via FTP img file for Pi 5 to ".update" folder
- create in ".update" folder ".nocompat" file
- turn off
- Plugin USB Stick into PI 5 - restart
- Hope