promtail: transform the whole log line based on regex - grafana-loki

Question

I'm having some challenges with coercing my log lines in a certain format.
I'm running one promtail instance on several log files, of which some are logfmt and others are free-form.
My objective is to transform the free-form ones to the same logfmt as the others, independent of any other labeling. That means the actual payload (log line) pushed to my qryn instance is then supposed to have the same format, and I woudn't even be able to "see" the original, free-form log line downstream. This should enable me to use a simple | logfmt in grafana, regardless of the log source.
I tried in several ways, but I can't get the log line replaced, i.e. while I can extract to labels in all ways conceivable, I can't replace the actual log line.
A (slightly redacted) promtail-config.yml:
server:
disable: true
positions:
filename: ${RUNDIR}/.logs/positions.yaml
clients:
- url: http://mylocalqryn:33100/loki/api/v1/push
batchwait: 5s
timeout: 30s
scrape_configs:
- job_name: consolidated-logs
# https://grafana.com/docs/loki/latest/clients/promtail/pipelines/
# https://grafana.com/docs/loki/latest/clients/promtail/stages/template/
pipeline_stages:
- match:
selector: '{ Program="freeformlog" }'
stages:
- regex:
expression: '^(?P<time>^[0-9-:TZ.+]*)\s+(?P<level>[A-z]*)\s+(?P<Function>[0-9A-z:.]*)\s+(?P<msg>.*$)'
- timestamp:
format: RFC3339
source: time
- template:
source: level
template: '{{ ToLower .Value }}'
- labels:
level:
msg:
Function:
- replace:
expression: '.*'
replace: 'time="{{ .timestamp }}" level="{{ .level }}" msg="{{ .msg }}" Host="{{ .Host }}" Program="{{ .Program }}" Function="{{ .Function }}"'
static_configs:
- targets:
- localhost
labels:
Host: ${HOST:-"_host-unknown_"}
Program: logfmtcompat
__path__: ${RUNDIR}/.logs/logfmtcompat.log
- targets:
- localhost
labels:
Host: ${HOST:-"_host-unknown_"}
Program: freeformlog
__path__: ${RUNDIR}/.logs/freeformlog.log