When attempting to start on a rpi4, I get the following:
(I can see prometheus.yml appears as a directory, shouldn't it be a file?)

$docker-compose up -d

Starting thermos ...
grafana is up-to-date
Starting prometheus ...
Starting prometheus ... error

ERROR: for prometheus Cannot start service prometheus: OCI runtime create failed: container_linux.go:367: starting container process caused: process_linux.go:495: container init caused: rootfs_linux.go:60: mounting "/home/pi/thermos/prometheus-config/prometheus.yml" to rootfs at "/var/lib/docker/overlay2/c3c864144053702b48098435fe3c50f064c01728deb2cf704a1770db6f2a81cd/merged/etc/prometheus/prometheus.yml" caused: not a directorStarting thermos ... done
h exists and is the expected type

ERROR: for prometheus Cannot start service prometheus: OCI runtime create failed: container_linux.go:367: starting container process caused: process_linux.go:495: container init caused: rootfs_linux.go:60: mounting "/home/pi/thermos/prometheus-config/prometheus.yml" to rootfs at "/var/lib/docker/overlay2/c3c864144053702b48098435fe3c50f064c01728deb2cf704a1770db6f2a81cd/merged/etc/prometheus/prometheus.yml" caused: not a directory: unknown: Are you trying to mount a directory onto a file (or vice-versa)? Check if the specified host path exists and is the expected type
ERROR: Encountered errors while bringing up the project.

Still got a few things that need (re)configuration:
This was on a fresh Pi4

pi@raspberrypi:~/thermos $ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
e8dc6cb2231a ghcr.io/truncj/thermos:latest "python -u main.py" 4 minutes ago Restarting (1) 11 seconds ago thermos
c4a98e66340a grafana/grafana "/run.sh" 4 minutes ago Restarting (1) 34 seconds ago grafana
b7cf14bb5648 redis:6.0.12-alpine "docker-entrypoint.s\u2026" 4 minutes ago Up 4 minutes redis
d11ab7633163 prom/prometheus-linux-armv7 "/bin/prometheus --c\u2026" 4 minutes ago Restarting (2) 33 seconds ago prometheus

pi@raspberrypi:~/thermos $ docker logs --follow thermos
Traceback (most recent call last):
File "main.py", line 15, in
from devices import Thermostat
File "/app/devices.py", line 10, in
from w1thermsensor import W1ThermSensor, NoSensorFoundError
File "/app/venv/lib/python3.7/site-packages/w1thermsensor/init.py", line 8, in
from .core import W1ThermSensor # noqa
File "/app/venv/lib/python3.7/site-packages/w1thermsensor/core.py", line 531, in
load_kernel_modules()
File "/app/venv/lib/python3.7/site-packages/w1thermsensor/core.py", line 525, in load_kernel_modules
raise KernelModuleLoadError()
w1thermsensor.errors.KernelModuleLoadError: Cannot load w1 therm kernel modules

pi@raspberrypi:~/thermos $ docker logs --follow grafana
GF_PATHS_DATA='/var/lib/grafana' is not writable.
You may have issues with file permissions, more information here: http://docs.grafana.org/installation/docker/#migrate-to-v51-or-later
mkdir: can't create directory '/var/lib/grafana/plugins': Permission denied

pi@raspberrypi:~/thermos $ docker logs --follow prometheus
level=info ts=2021-04-20T03:56:03.773Z caller=main.go:380 msg="No time or size retention was set so using the default time retention" duration=15d
level=info ts=2021-04-20T03:56:03.774Z caller=main.go:418 msg="Starting Prometheus" version="(version=2.26.0, branch=HEAD, revision=3cafc58827d1ebd1a67749f88be4218f0bab3d8d)"
level=warn ts=2021-04-20T03:56:03.774Z caller=main.go:420 msg="This Prometheus binary has not been compiled for a 64-bit architecture. Due to virtual memory constraints of 32-bit systems, it is highly recommended to switch to a 64-bit binary of Prometheus." GOARCH=arm
level=info ts=2021-04-20T03:56:03.774Z caller=main.go:423 build_context="(go=go1.16.2, user=root@978f8f2e1ea7, date=20210331-11:56:37)"
level=info ts=2021-04-20T03:56:03.774Z caller=main.go:424 host_details="(Linux 5.10.17-v7l+ #1403 SMP Mon Feb 22 11:33:35 GMT 2021 armv7l raspberrypi (none))"
level=info ts=2021-04-20T03:56:03.775Z caller=main.go:425 fd_limits="(soft=1048576, hard=1048576)"
level=info ts=2021-04-20T03:56:03.775Z caller=main.go:426 vm_limits="(soft=unlimited, hard=unlimited)"
level=error ts=2021-04-20T03:56:03.776Z caller=query_logger.go:87 component=activeQueryTracker msg="Error opening query log file" file=/prometheus/queries.active err="open /prometheus/queries.active: permission denied"
panic: Unable to create mmap-ed active query log

When I use docker-compose up -d I get:

ERROR: for 0500c116a4ac_prometheus "host" network_mode is incompatible with port_bindings
ERROR: for grafana "host" network_mode is incompatible with port_bindings
ERROR: for prometheus "host" network_mode is incompatible with port_bindings

docker compose version 1.29.0

It seems you can't use network_mode = host when specifying ports?