Booting latest master on Turris 1.x results to:

=> boot
BOOT NAND
reading zImage
3330788 bytes read in 170 ms (18.7 MiB/s)
wdt status 00000003
reading fdt
13143 bytes read in 14 ms (916 KiB/s)
WARNING: adjusting available memory to 30000000
## Booting kernel from Legacy Image at 02100000 ...
   Image Name:   Linux-4.19.56
   Created:      2019-07-01   0:02:57 UTC
   Image Type:   PowerPC Linux Kernel Image (gzip compressed)
   Data Size:    3330724 Bytes = 3.2 MiB
   Load Address: 00000000
   Entry Point:  00000000
   Verifying Checksum ... OK
## Flattened Device Tree blob at 02000000
   Booting using the fdt blob at 0x2000000
   Uncompressing Kernel Image ... Error: Bad gzipped data
gzip compressed: uncompress error -1
Must RESET board to recover

This is most probably just an invalid format of kernel. We should fix that in turris1x-support package.