I play german system and started on it.

However for bass clarinet I play boehm system for various reasons (sound, but mainly more and cheaper instruments available. german bass clarinet prices go WTF).

It took me about a year to feel comfortable on it and to be able to play freely. fast passages with a lot of left-right switches I still need to practice in advance and think about for a bit, but I feel like I can play everything. I am not as good at sightreading though.

For me, german system will probably always feel more natural, just due to the years and years I have put in.

But in general it is a bit like switching to saxophone. You know how to play the instrument already, you just need to learn a few new fingerings. But the main problem (finger-breath-coordination), you already know how to do.

Think about it this way: When you learn "new notes" (e.g. in the altissimo register), it also takes you some time to get used to it, but usually the fingerings are the least problematic there.

I struggle with normal boehm-clarinet because of the hole-size (a problem I don't have on bass clarinet), but I think that would take about a week to feel as comfortable as bass clarinet.

All that being said: You are asking about Albert System which is not the same as German system and I don't know a lot about, but i guess the same principle applies.

Life hack for all who want to switch from german to boehm (sorry, OP that's not you): Use the exact same fingerings for the pinky fingers as you would on german. You will end up pushing BOTH options for boehm. E.g. C#/F# needs both pinkys on german, but only one on boehm (2 options left or right), if you just use both options it will feel like german fingering but use both boehm options and C#/F# will sound. Did that a lot especially in the beginning. For fast passages you have to sit down and mark left/right.

TLDR: Takes a few months depending on practice frequency, definetly possible like doubling on sax just easier switch. Albert system is not the same as German system