preferring OSPF inter-area compared to intra-area

hello everybody..

I've decided to drop this question here in Gs since I'm confused and not
able to understand this scenario.

I would like to filter an OSPF intra-area route in this scenario.

=============VL0===VL1=
22222222222211111444444
R3 - SW1 - R6 - R1 - R3

from R3 to R6 there is Area2
from R6 to R1 there is Area1
from R1 to R3 there is Area4
R1, R3 and others are in Area0
There is a VL between R6 to R1 and from R1 to R3

R3 LO is on Area2.
What I want to do is configure some filtering in R6 that allows me to reach
R3 L0 through path R6->R1->R3
Without filtering I reach R3 L0 via R6->SW1->R3 since it's an intra-area
route.
If I shut down the link between R6 and SW1 I can reach R3 L0 via
R6->R1->R3 (this is an inter-area route and this means VLs are working)
my requirement: I want to filter on R6 so I would prefer inter-area instead
of intra-area.
As far as I know I cannot use :

- area x range command: since this filters type3 between areas
- distribute-list: since I've to filter based on a source also and I cannot
do with it
- only valid solution looks using a route-map matching prefix-list and
something else.
  - I've tried this solution matching prefix list R3 L0 and ip route-source
and doesn't work
  - I've tried same as above but matching interface (interface between R3
and SW1)
  - I've tried same as above but matching a tag but I don't understand how
to tag a route 'out' with ospf.

Is there something easier to filter this type 1 LSA into R6? Or to prefer
inter area compared to intra ones?

thanks

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