Beta test firmware for the Flip5 has been released for Europe and the U.K. to all those eligible and enrolled in the Samsung Beta test programme via the Samsung Members app. See screenshot #1.
Eligibility for Beta depends on your device's, F731B, current firmware, F731BXXU1AWI3, and your CSC codes which should be for European stock Samsung, non carrier branded devices, EUX. To locate your devices CSC code, go to...
Settings > About phone > Software information > Service provider software version
Screenshot #1 Beta enrollment (N.B. This is for the Fold5)
Screenshot #2 Service provider software version (N.B. This is a Fold5 version)
Beta test firmware release for Flip5, EUX.
If your device meets all the previous requirements and you have still not received the Beta Test banner in your Samsung Members app, try the following...
- Uninstall the Samsung Members app in the Galaxy Store app.
- Turn off Wi-Fi
- Reboot device
- Go to Galaxy Store and reinstall the Samsung Members app
- Reboot device and turn Wi-Fi on and check in Samsung Members app for One UI 6.0 enrolment banner.
Be advised that places on the Beta test are limited and there are reports from some regions that applications have been closed.
E&OE
I've tried that and still no beta option 
