The trick is to understand when the pattern stops alternating and to try and keep up with it as well as possible. No simple pattern by any means.

Note that for almost the entirety of the first phase of the pattern you want to strictly alternate, which will mean you will want to stretch left thumb to the 4th lane to hit 2 notes.

After this, it is your queue that the first half of the pattern has ended, left thumb returns to the middle lane the 3/2 split commences. Inclusive of the first middle lane note, the rhythm is LRLLLRLRLRLLLRL(L+R)