Hi, I’d maybe do turntable > phono amp > Echo Link > powered speaker in case the Link’s line in needs a higher level than the turntable.
For the line in redistribution to an Alexa multi room music (MRM) group, the Link itself needs to be part of the group and the MRM group identified under “Devices> Echo & Alexa> Echo Link> select Line in distribution” in the Alexa app. Once you start playing, the Link should detect the audio then send it to the other echos. The Amazon help pages on this seem to wander around and I can’t find them, but these links should help
Amazon Digital and Device Forum United States
www.amazonforum.com
I’m not 100% sure if the Link can do line in distribution and line out at the same time - again, the documentation is very sparse if it even exists. However, given that WiiM devices can be part of an MRM group, include yours in the group with the Link and other echos and take its line out into your speakers.
Let us know how you get on once you get your head around the above - the Link can be a mysterious beast to understand and for ages I wondered just what it was meant to do…