As pointed out by Jürgen in twsapi group on groups.io,
"The archived ib_insync implements features equivalent to those available in IBKR supplied TWS API Version 10.25 (MaxClientVersion 178, September 2023) and is already slightly behind the latest Version 10.27.01.
For example, ib_insync clients cannot take advantage of the 17 additional fields in the Contract class that were introduced for SecType FUND instruments in API Version 10.26. And that gap will slowly widen, unless these modifications can be made to the source code, thoroughly tested, and released as binary packages. The latest TWS/IBGW just switched to 10.28 and Beta is at 10.29."
Shame that the groups.io forum is apparently toasted. Anyway, was just browsing around and found this commit which may be similar enough to serve as a jumping off point.
As pointed out by Jürgen in twsapi group on groups.io, "The archived ib_insync implements features equivalent to those available in IBKR supplied TWS API Version 10.25 (MaxClientVersion 178, September 2023) and is already slightly behind the latest Version 10.27.01.
For example, ib_insync clients cannot take advantage of the 17 additional fields in the Contract class that were introduced for SecType FUND instruments in API Version 10.26. And that gap will slowly widen, unless these modifications can be made to the source code, thoroughly tested, and released as binary packages. The latest TWS/IBGW just switched to 10.28 and Beta is at 10.29."