Ethernet to WiFi File Sharing Painfully Slow

Most likely your Wi-Fi network is malfunctioning, or encountering interference.

Near as I can tell, Linksys uses the name “Velop” to mean “mesh node”. They offer a lot of mesh nodes, too.

You’ll need to investigate your mesh network and its settings.

Do you have the mesh nodes connected directly to your ISP, or is there an ISP-provided box also involved?

On Mac, the basic Wi-Fi environment characteristics are visible when using Option-Click on the Wi-Fi logo 🛜 in the menu bar to capture some Wi-Fi network data.

For us to look at the Wi-Fi network data here, post the items shown in the following image including the Security mode and from Channel to NSS inclusive (Security, Channel, Country, RSSI, Noise, Tx Rate, PHY mode, MCS, NSS, green highlight) (without posting the Wi-Fi address, any local HotSpots that might be present, the network name, or the BSSID, all of which are expurgated from the image shown below, red highlight), and we can take a look at the basic network environment.

(Info from both ends would be helpful, too.)

Tools such as the third-party WiFi Explorer app for macOS can be used to get a better view of the Wi-Fi environment.

Your particular Wi-Fi gear might also have some built-in network monitoring capabilities.

VPNs don't have to be active to affect internet speeds. They have several supporting files that get activated when the Mac is booted even though the primary app isn't. Unless you're using a true VPN tunnel, such as between you and your employer's, school's or bank's servers, they provide false security from a privacy standpoint.  Read these articles:  Pubic VPN's are anything but private and Security Risks: The Dangers of Using Free VPNs (eccu.edu).    

Additionally a new study ("Apple Offers Apps With Ties to Chinese Military”) is specifically about VPN apps in Apple’s App Store.

You can check to see if you've removed all of the supporting files by downloading and running the shareware app Find Any File to search for any files with the application's or the developer's name in the file name.  For your VPN software you'd do the following search(es): 

1 - Name contains vpn

2 - Names contains "your VPN app name"

Any files that are found can be dragged from the search results window to the Desktop or Trash bin in the Dock for deletion.

FAF can search areas that Spotlight can't like invisible folders, system folders and packages.  

If you get warnings that the file can't be deleted because it is in use or used by another app boot into Safe Mode according to How to use safe mode on your Mac and delete from there.

Note:  if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode.  This makes it act as a wired keyboard as will assure a successful boot into Safe Mode.

Too many of the “coffee shop” VPNs are seemingly written to collect metadata, and to not have completely unacceptable performance. Both goals are not always met.

Remove the VPNs, and test again. Even a supposedly-idle VPN can degrade performance.

If there are add-on anti-malware apps installed here, remove all that and test again, too.

And please post your Wi-Fi configuration data, as well.

Are the first 3 digits of both IPs the same?

But you're using WiFi in the transfer and the VPNs can affect it.

Unless your employer, bank or school requires a VPN to access their servers it's only slowing down the speed. It's not needed so get rid of it.

Whether this is the VPN or other add-on security apps, or potentially the ISP box is not configured in bridged mode, or there is signal interference, or something else? Donno.

But I’m clearly not able to get this thread moving forward, and will accordingly be unfollowing the thread.

Do you have a VPN app on any of the devices in question?