Hello Philip,
As far as I know there is no known vulnerability on the RDP of the STM32U5.
The link you provide concerns old STM32 that were designed before the glitching attacks became common and also when security was not yet a bit concern.
The STM32U5 was certified SESIP Level 3 with board level robustness.
Most of the new STM32 devices have or will get soon the certification.
You can have a look to this page showing which products have a certification.
You can find certificates details in TrustCB page here.
Regarding the STM32 that have no such certification, you can check the ST PSIRT page here
where you will find all the security bulletins and advisories.
In particular TN1489-ST-PSIRT that addresses all STM32 that don't have any certification:
"Regarding STM32 products and their resistance to physical attacks:
Unless an STM32 product is SESIP or PSA certified as having a security assurance level covering physical attacker
resistance, it may be vulnerable to physical attacks"
In conclusion, STM32U5 is not concerned by the attack you mention.
Best regards
Jocelyn
