To see if there is a cheaper solution than the CFexpress card type B for the Canon EOS R5, I bought the CFexpress To SSD Converter from Zitay.
And a separate 2TB Samsung 980 Pro PCIe 4.0 NVMe M.2 SSD drive.
In total, it is still much cheaper then, for example, a Sony Tough 512 GB CFexpress card (For me 6.2 times in terms of storage capacity).
Now I can shoot 8K RAW footage up to the time limit of 29:59 minutes without getting an overheating warning!