To install Magisk you need to extract boot img, patch the img through Magisk app and flash the patched img through fastboot
That is RECOMMENDED method for installing Magisk - instead of ancient 'guides' please read the OFFICIAL Magisk documentation on GitHub
Nevertheless, you can still install Magisk through custom recovery, but you need one that is compatible for your device and ROM
For Lisa, MIUI 13 / A 12, look for the other thread here, Orange Fox (unofficial) recovery. OF is good recovery and it works - ie, it properly supports Storage encryption on MIUI 13 / A 12.
And carefully read instructions how to install - installation of custom recoveries is no more that simple as in the old times - if you fastboot flash ... you will brick your device
But again. To install Magisk you don't need custom recovery. Custom recovery breaks OTA (for the stock ROM). And there are better options for backup (eg Swift Backup root app) - nandroid restore may brick the device or you loose DRM L1, or so
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Personally, I have switched (for my Lisa - aka Mi 11 Lite 5G NE) from stock to Xiaomi eu (in short, it is kind of debloated MIUI)
Since it's not stock, it requires custom recovery to install. And yes, I use the mentioned Orange Fox
In fact, Xiaomi.eu requires custom recovery as well for upgrades (kind of 'OTA' upgrades), hence they pack that same Orange Fox into their Xiaomi.eu, Stable and Weekly ROM installations
Ie, it also proves that the mentioned OF is good for Lisa, for MIUI 13/A 12
And frankly, I've tried few other custom recoveries for Lisa, A12, but something did not work or did not work as smooth as with the mentioned OF
And of course I do root (stock and now Xiaomi.eu), but although I could do that through OF, I prefer what is the official way by patching and flashing
In fact, once you first time install Magisk, you can later update Magisk much easier - again through the Magisk app, you take Install, choose Direct method, it will update Magisk and reboot to take in effect - all without the need for custom recovery or fastboot
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And some 'theoretical' insights. Lisa is A/B device, with Recovery integrated into the Boot partition, and of course (as other devices launched with A11 or A12) read-only SAR
Read-only SAR means that System (+ Vendor, Product ..) is read-only on the file system level. Even with the root you cannot write / make changes to the system partitions - but Magisk provides the so-called systemless rooting where it mounts the required changes over System in boot time. That's the way all modern Magisk modules work (incl. eg Systemless hosts for AdAway)
Hence no practical limitations here
Recovery is integrated into the Boot partition. Hence no Recovery partition. Therefore, a more complicated installation for custom recoveries - but follow the guides (not ancient ones but eg the guide in that OF thread here)
And although Recovery is integrated into the Boot, it is still possible to have both the custom recovery (like that OF) and Magisk. They both install to the same Boot partition.
And from the practical point of view - no problem, normal boot boots to the rooted MIUI, boot with Vol+ boots to OF (as usual)
A/B means that device comes with two slots A and B. Ie, the whole SAR (System partitions) and Boot is duplicated. Eg, there is boot_a, boot_b, system_a, system_b, etc (but of course data partition is single)
A/B makes OTA upgrades (for stock ROM) more seamless for the user - you can Google about how it works
But again, no problem with all that to install Magisk, OF, custom ROMs - one just needs to read, learn and stay up-to-date
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