• 'Talk against' means to publicly express opposition, criticism, or disagreement regarding a person, policy, or idea. It involves voicing negative opinions or arguments to counter a particular viewpoint, often in a debate or to highlight faults.

But the source of the above would be queried or worse by some contributors.

The fact is, the string (probably better analysed as verb + preposition rather than multiword verb / phrasal verb) is far less common (as Mark Foskey says) than 'speak against'. The only relevant reference I have found is as a definition rather than being defined:

• Complain To:

Today, let us study the phrasal verb ‘Complain To’, which we often find in common parlance. We shall discuss its meaning and use in a number of sentences. Though it is not a phrasal verb in the conventional sense, it is used with this specific preposition.

Meaning —

• To talk against something or someone before an authority.

[Atmaja Bandyopadhyay, Department of Law, University of Calcutta; Quora]

So the strings picked out below

• Joan spoke against the new regulations.
• Ali talked against the way the legislation against immorality was gradually weakening.
• Tom complained to the board about several aspects of his treatment.

are all 'not phrasal verbs in the conventional sense'

(ie are analysed as [verb] + [preposition] {then + prepositional; complement}

rather than [verb + particle] + [noun phrase], ie not as multiword verbs.

But they do select for specific prepositions.

'Talk against ...' is acceptable, but not exactly idiomatic; 'speak against' would normally seem the more natural choice.

• 'Talk against' means to publicly express opposition, criticism, or disagreement regarding a person, policy, or idea. It involves voicing negative opinions or arguments to counter a particular viewpoint, often in a debate or to highlight faults.

But the source of the above would be queried or worse by some contributors.

The fact is, the string (probably better analysed† as verb + preposition rather than multiword verb / phrasal verb) is far less common (as Mark Foskey says) than 'speak against'. The only relevant reference I have found is as a definition rather than being defined:

• Complain To:

Today, let us study the phrasal verb ‘Complain To’, which we often find in common parlance. We shall discuss its meaning and use in a number of sentences. Though it is not a phrasal verb in the conventional sense, it is used with this specific preposition.

Meaning —

• To talk against something or someone before an authority.

[Atmaja Bandyopadhyay, Department of Law, University of Calcutta; Quora]

[In all honesty, the definition leaves a lot to be desired; the complements of 'against' and 'to' here are of course quite different. However, the required string is taken as acceptable.]

So the strings picked out below

• Joan spoke against the new regulations.
• Ali talked against the way the legislation against immorality was gradually weakening.
• Tom complained to the board about several aspects of his treatment.

are all 'not phrasal verbs in the conventional sense'

(†ie are analysed as [verb] + [preposition] {then + prepositional; complement}

rather than [verb + particle] + [noun phrase], ie not as multiword verbs.

But they do select for specific prepositions.

'Talk against ...' is acceptable, but not exactly idiomatic; 'speak against' would normally seem the more natural choice.