[Firmware Bug]: Bootloader left irq enabled: bank 1 irq 9

Hi and hello to you all,

I just wanted to install ubuntu mate 20.04 onto my Raspi 3B+ on a new 32 GB SD-card.
I downloaded releases.ubuntu-mate.org/focal/arm64/ubuntu-mate-20.04.1-desktop-arm64+raspi.img.xz.
My PC runs on ubuntu 20.04 LTS as well, so I just clicked on the img.xz-archive and transferred it to the SD card.
Raspi starts booting, then prints the two following lines:
[0.000000] [Firmware Bug]: Bootloader left irq enabled: bank 1 irq 9
[1.998677] spi-bcm2835 3f20400.spi: could not get clk: -517
Then it shows the GUI splash screen, after approx. a minute, I am redirected to

Other SD cards with other OSes boot perfectly, so I assume there is no hardware issue.
I found absolutely nothing regarding these messages.

Does anyone please have a helpful hint?

Many thanks,

Have you solved the problem?
I meet exactly the same situation with you.