This is a link to the latest MAN ES service letter on biofuel operation (July 2023).
It addresses important technical matters related to the operation of two stroke engines on biofuel in a concise way.

It is worth noting the below paragraph in page 4:
Biofuel analysis and standards
At the time of writing, there is no international marine fuel standard for biofuels. Until then other fuel standards as ISO 8217 and additional fuel analysis methods have to be used. Interpretations and evaluation of the results should be carefully made. In the current ISO 8217:2017, HVO (up to 100%), and FAME (up to 7%) are included in certain distillate grades (Table 1 in ISO 8217:2017). FAME mixed with residual fuel is not included. There is no analysis method in ISO 8217:2017 for
measuring FAME contents above 7%. Note that insurances, warranties, and contracts may
include clauses on ISO 8217 compliance and that biofuel may not be included in these. A fuel is considered to be ISO 8217 compliant if it adheres to the standard in its entirety. If a fuel has characteristics within the limits of, for example, Table 2 RM-grades in ISO 8217,
but includes bio-components not covered in ISO 8217, then ISO 8217 compliance cannot be claimed.”


It looks like there is currently a gap in the ISO 8217 that must be closed the soonest because biofuels are becoming an increasingly popular short term/intermediate solution for the decarbonization of the shipping sector.