I updated my system and it broke again. Had some trouble getting it to work again. For some reason the DTS editor doesn't come up in armbian-config anymore(?). Anyway, it can be done from the console. I decompiled the sun501-h6-orangepi-3-lts.dtb, edited it and compiled it again. It worked as a charm. I noticed that the spi pins had changed to 0x31 and 0x32 and the spi@5011000 phandle was 0x78 instead of 0x7a.
I only changed status to "okay" and added the spidev@0 {...} section. Then I removed the dtbo overlay.
spi@5011000 {
compatible = "allwinner,sun50i-h6-spi\0allwinner,sun8i-h3-spi";
reg = <0x5011000 0x1000>;
interrupts = <0x00 0x0b 0x04>;
clocks = <0x06 0x53 0x06 0x51>;
clock-names = "ahb\0mod";
dmas = <0x2e 0x17 0x2e 0x17>;
dma-names = "rx\0tx";
pinctrl-names = "default";
pinctrl-0 = <0x31 0x32>;
resets = <0x06 0x20>;
status = "okay";
#address-cells = <0x01>;
#size-cells = <0x00>;
phandle = <0x78>;
spidev@0 {
compatible = "armbian,spi-dev";
reg = <0x00>;
spi-max-frequency = <0xf4240>;
};
};