With the option for update via adb you can likely use adb commands while phone is in recovery and connected to a computer.
first you will need the adb files:
unzip the contents to computer. I recommend root of drive i.e. C:\adb.
next you will need USB drivers to connect phone to computer and be able to execute commands:
Install drivers via usual windows methods.
got to folder where you extracted adb files
hold left shift key and right click mouse
select open command window here.
connect phone to computer and boot to recovery.
you should get output for server starting and a line showing phones serial number if connection is possible.
Providing all is well:
adb pull /sdcard/.
this should pull all contents on internal sdcard to current directory.
This will NOT retrieve data stored elsewhere such as phone logs or text messages or contacts. Unfortunately those will be lost without the option to recover from boot loop. It will only recover data saved on data partition in phone such as photos, music and other misc info saved there by apps.
Try wipe cache partition to see if that gets past boot loop. only option I can think of.
Or simply flash custom recovery like twrp that allows access to external sdcard