“Per tagliare la testa al toro” (how to fix things once and for all) [I hope], or “Couper la tête du serpent” I suggest not to confuse L5 GPS with E5a of Galileo and B2a of Beidu…
To stay on the LC29H module It is able to process the following RTCM Messages
RTCM v3.2 MSM7:
1097 GALILEO MSM7 containing data E1 and E5a, E5b and E5(a+b)
1127 Beidou MSM7 containing data B1 and B2
1077 GPS MSM7 containing data L1 C/A, L2 C and L1/L2 P(Y)
1087 GLONASS MSM7 containing G1 and G2 C/A data
for RTCM v3.2 MSM4:
1074 GPS MSM4 containing data L1 C/A, L2 C and L1/L2 P(Y)
1084 GLONASS MSM4 containing G1 and G2 C/A data
1094 GALILEO MSM4 containing E1 and E5a, E5b and E5 data (a+b)
1124 Beidou MSM4 containing B1 and B2 data
As you can see the module can receive L1C/A and L5C i.e L5 Q but only processes L1C/A for ambiguity determination, while processing E5a and B2 messages for Calculation to determine ambiguity.
In practice it does not use L5 GPS signals as it does not receive the equivalent rtcm messages…