Hello, I'm also experiencing a nasty memory leak with LE on RPi 4B 4Gb.
I've a similar setup as OP, where I've the RPi connected to a LG TV alongside a Denon Receiver with HDMI ARC (not sure if that's relevant, I've only just started to investigate the problem).
I've tried setting MALLOC_ARENA_MAX=8 as mentioned in this forum but it hasn't resolved nor mitigated the problem.
I've managed to blacklist UAS for my USB3 SCSI adaptor by adding usb-storage.quirks=aaaa:bbbb:u where aaaa is idVendor and bbbb is idProduct to /flash/cmdline.txt.
Result:
[ 0.876579] usbcore: registered new interface driver usb-storage
[ 1.490557] usb 2-2: UAS is blacklisted for this device, using usb-storage instead
[ 1.490608] usb 2-2: UAS is blacklisted for this device, using usb-storage instead
[ 1.490615] usb-storage 2-2:1.0: USB Mass Storage device detected
[ 1.490905] usb-storage 2-2:1.0: Quirks match for vid 0080 pid a001: 800000
[ 1.490965] scsi host0: usb-storage 2-2:1.0